1. Field of the Invention
This invention pertains generally to power plants; and more particularly to high efficiency, low cost, and readily scaled biomass power generation systems. The power generation system incorporates a change of state of a fraction of the motive fluid responsive to externally applied heat. Motive fluid rises in a column owing to decreases density and kinetic energy transfer from gaseous phase bubbles therein. When fully elevated, the motive fluid then drives a gravity motor by the weight of the pumped water and condensed vapor to generate electricity.
2. Description of the Related Art
Approximately ninety percent of electric power generation is accomplished within the United States by burning combustible fuels to produce steam, and using the steam to drive a steam turbine. The fuels are mined or pumped from the earth, and represent a progressively more scarce resource. In order to most economically extract and utilize these anciently created fuels, modern power production is accomplished on a very large scale through enormous mining and drilling equipment, massive trains and pipelines for the transport of the fuel, and enormous centralized power plants. Unfortunately, these conventionally fueled power plants are not well adapted to the use of more renewable resources such as biomass.
Combustible matter will be understood to encompass a wide variety of flammable materials. With proper design consideration, many combustible materials may be used to generate the heat necessary to produce electrical energy. Furthermore, there are quite consequential and renewable sources of combustible materials that could be used to produce electricity. In the context of the present invention, a preferred source of combustible matter is agricultural biomass of otherwise little value. A good example are corn cobs, which are the byproduct of harvesting field or seed corn. These cobs are difficult to comminute, extremely slow to compost, and add little nutritional value to silage or other animal feed. However, since field corn is typically dried prior to storage, and often in the field to as great an extent as possible, these cobs can be quite dry as a normal part of the growing and harvesting process. They can provide significant energy upon combustion, and so have been recognized as a useful biomass source for energy production. Other similar biomass materials include many seed hulls, such as but not limited to peanut hulls and sunflower seed hulls.
As is known in the forestry and agricultural industries, transportation of relatively low-value biomass such as corn cobs, hulls, mixed or contaminated biomass, and the like is particularly difficult and generally quite expensive. Transportation costs tend to be relatively high due to the difficulty loading and unloading of biomass, which may be quite diverse in size and weight. Furthermore, the relatively high volume but low density material takes up substantial space, while containing relatively little combustible or otherwise usable matter. In contrasty, coal and oil are extremely energy dense. As a result, there has not been a particularly cost-effective way to transport many of these agricultural by-products to a central facility such as a centralized power plant.
Heretofore, these biomass materials such as corn cobs have primarily been burned for the sole purpose of providing heat to buildings and other similar static structures. This allows forestry and agricultural biomass to be converted to energy at the source farm, without requiring transportation over the roadways to a secondary generation location. This conversion to heat is definitely beneficial, and these cobs, hulls, and the like serve as a completely renewable resource. However, this is only of benefit for those establishments that have a need for large quantities of heat.
Unfortunately, for the relatively larger farms, the use of the available biomass for heat often will exceed the demand for heat by the farm. Furthermore, and particularly in more temperate climates, there may be relatively little heat required at all, other than for drying or to heat water or for quite limited other applications. As a result, the biomass available to an agricultural or forestry operation is substantially under-utilized today.
The conversion of heat to electricity has long been studied and refined, with many different techniques proposed and implemented over the years. In addition to the most prevalent steam turbines, various density-based turbines have been developed. Exemplary expansion-contraction container patents, the teachings and contents which are incorporated herein by reference, include: U.S. Pat. No. 4,121,420 by Schur, entitled “Gravity actuated thermal motor”; U.S. Pat. No. 6,978,610 by Carnahan, entitled “Reversible heat engine”; and U.S. Pat. No. 8,875,513 by Paya Diaz, entitled “Thermal energy conversion plant”.
Another density-based turbine type operates through the substantial displacement of liquid with gas or steam. Exemplary patents that resemble the modern steam turbine, the teachings and contents which are incorporated herein by reference, include: U.S. Pat. No. 196,759 by Miller, entitled “Process for utilizing mercury as a motive power”; U.S. Pat. No. 1,343,577 by Okey, entitled “Heat-engine”; U.S. Pat. No. 2,265,878 by Stoker, entitled “Power apparatus”; U.S. Pat. No. 4,187,686 by Pommier, entitled “Power generator utilizing elevation-temperature differential”; U.S. Pat. No. 4,192,145 by Tanaka, entitled “Process for utilizing energy produced by the phase change of liquid”; U.S. Pat. No. 4,232,524 by Goyat, entitled “Production of industrial electrical energy from hydraulic energy”; U.S. Pat. No. 4,255,933 by Bailey et al, entitled “Geothermal power producing loop”; U.S. Pat. No. 4,372,123 by Austin, entitled “Thermal-gravity engine”; and U.S. Pat. No. 8,393,153 by Wolter, entitled “Method, device, and system for converting energy”. Other similar exemplary pressure transport patents, the teachings and contents which are incorporated herein by reference, include: U.S. Pat. No. 3,983,704 by McFarland, entitled “Solar operated thermodynamic drive”; U.S. Pat. No. 243,909 by Iske, entitled “Motor”; and U.S. Pat. No. 7,694,515 by Miller, entitled “Engine”.
Intermediate between steam and displacement are bubble-driven turbines. Exemplary patents, the teachings and contents which are incorporated herein by reference, include: U.S. Pat. No. 144,883 by Beekman, entitled “Steam engines”; U.S. Pat. No. 169,269 by Johnson, entitled “Rotary steam-engine”; U.S. Pat. No. 3,715,885 by Schur, entitled “Heat vapor differential engine”; U.S. Pat. No. 3,916,626 by Schur, entitled “Thermally powered generating system employing a heat vapor bubble engine”; U.S. Pat. No. 3,934,964 by Diamond, entitled “Gravity-actuated fluid displacement power generator”; U.S. Pat. No. 4,038,826 by Shaw, entitled “Solar energy system utilizing buoyancy as a conversion force”; U.S. Pat. No. 4,054,031 by Johnson, entitled “Power unit”; U.S. Pat. No. 4,141,218 by Rayboy, entitled “Buoyancy operated Sunmill”; U.S. Pat. No. 4,196,590 by Fries, entitled “Vapor buoyancy engine”; U.S. Pat. No. 4,363,212 by Everett, entitled “Buoyancy prime mover”; U.S. Pat. No. 4,498,294 by Everett, entitled “Buoyancy prime mover with pressure control means”; U.S. Pat. No. 5,685,147 by Brassea, entitled “Buoyancy and thermal differentials energy generator”; and U.S. Pat. No. 8,453,443 by Kim, entitled “Engine for energy conversion”.
Bubble transport engines that are not a typical gas pressure driven turbine, and instead rely upon the motion and density of bubbles to move the working fluid, may further be divided into two groups. The first group use a single fluid that is boiled to form a gas. Exemplary patents, the teachings and contents which are incorporated herein by reference, include: U.S. Pat. No. 3,375,664 by Wells, Jr, entitled “Convection current power generator”; and U.S. Pat. No. 3,443,129 by Hammitt, entitled “Vapor-liquid cycle MHD power conversion”. Other artisans have incorporated one fluid into another. Exemplary patents, the teachings and contents which are incorporated herein by reference, include: U.S. Pat. No. 4,030,303 by Kraus et al, entitled “Waste heat regenerating system”; and U.S. Pat. No. 6,412,281 by Cover, entitled “Methods and apparatus for generating hydrodynamic energy and electrical energy generating systems employing the same”.
Other exemplary bubble transport patents, the teachings and contents which are incorporated herein by reference, include: U.S. Pat. No. 4,486,701 by Cover, entitled “Thermal energy conversion”; U.S. Pat. No. 4,571,534 by Cover, entitled “Energy conversion system with fermentation”; U.S. Pat. No. 4,767,938 by Bervig, entitled “Fluid dynamic energy producing device”; and U.S. Pat. No. 8,733,103 by Paya Diaz, entitled “Thermal energy conversion plant”.
Some of these systems are potentially applicable to the combustion of forestry and agricultural biomass, but each have suffered from one or another deficiency that has prevented wide spread adoption.
In addition to the foregoing patents, Webster's New Universal Unabridged Dictionary, Second Edition copyright 1983, is incorporated herein by reference in entirety for the definitions of words and terms used herein.